1. Field of the Invention
The present invention relates to a coupling structure of a drive shaft to a swash plate assembly in a variable capacity swash plate type compressor.
2. Background of the Related Art
A compressor in an air conditioner for vehicles selectively receives power transmitted via an engine crank pulley from an engine in order to suck in heat-exchanged refrigerant from an evaporator, compress refrigerant through linear reciprocating motion of a piston and then discharge refrigerant to a condenser.
In the variable capacity swash plate type compressor, an example of the prior art is disclosed in Korean Utility Model Registration No.2002-28619 published on Apr. 17, 2002.
As shown in FIGS. 1 and 2, a swash plate assembly 10 has a hub 11 and a swash plate 15. The hub 11 has a boss 12 with a drive shaft through-hole 13 for passage of a drive shaft 20. The through-hole 13 has angular and substantially rectangular inner surfaces defined by first vertical and horizontal sections 16 and 14. The boss 12 has a single pin hole 12a intersecting perpendicular with the through-hole 13 for the drive shaft.
The swash plate 15 has a coupling hole 15a coupled to an outer periphery of the hub 11, and a piston 40 is coupled to an edge of the swash plate 15 as shown in FIG. 1.
In the meantime, in the drive shaft through-hole 13 of the boss 12, the drive shaft 20 has outer surfaces defined by second vertical and horizontal sections 21 and 22 configured substantially identical with the inner surfaces of the drive shaft through-holes 13.
The second vertical section 22 of the drive shaft 20 has a single slot 23 in the axial direction for allowing slidable motion of a coupling pin 30 which is inserted through the pin hole 12a in the boss 12.
According to a conventional configuration of the drive shaft coupled to the swash as set forth above, the hub 11 is supported by the drive shaft 20 via coupling of the coupling pin 30 so that the rotation center of the swash plate assembly 10 moves along the drive shaft 20 without variation.
The drive shaft 20 has the slot 23 in the longitudinal direction, which is coupled to the coupling pin 30 which is supported by the boss 12 of the hub 11 so that the coupling pin 30 moves along the slot 23 as the inclination angle of the swash plate assembly 10 increases.
Therefore the hub 11 moves while pivoting along the drive shaft 20 without any variation of rotation center.
However, the prior art of the above construction has disadvantages as follows.
First, in order to minimize bending moment applied to the single coupling pin 30 when the rotary torque of the drive shaft 20 is transferred to the hub 11 of the swash plate assembly 10, and allow the inner surfaces of the drive shaft through-hole 13 to have a configuration capable of accepting the variation in inclination angle of the swash plate assembly 10 in respect to the drive shaft 20, and to stably support the drive shaft 20 in the angle-varied inclination position of the swash plate assembly 10, the drive shaft through-hole 13 has a substantially rectangular internal cross section and the drive shaft 20 partly has a substantially rectangular external cross section corresponding to the internal cross section of the drive shaft through-hole 13 to be inserted into the drive shaft through-hole 13. However, the prior art has drawbacks in that the cross sections of the drive shaft through-hole 13 and the drive shaft 20 are additionally formed into the rectangular ones and the swash plate assembly must be precisely processed in terms of an inclination angle of the swash plate assembly 10.
Second, the second vertical and horizontal sections 21 and 22 of the drive shaft 20 frictionally contact with the second vertical the first section 16 of the hub 11 by a large amount thereby poorly carrying out the variation in inclination angle of the swash plate assembly 10.
Third, the swash plate 15 of the swash plate assembly 10 is frequently twisted owing to compressive load of the piston 40 during actuation of the compressor. However, since this twist is not fundamentally prevented, it is impossible to vary the inclination angle of the swash plate in a more stable manner.
In the meantime, in the above variable capacity swash type compressor, other examples of the prior art include Japanese Patent Laid-open Publication No. Hei6-307333 published on Nov. 1, 1994 and Japanese Patent Laid-open Publication No. Hei8-14157 published on Jan. 16, 1996.
Even though the above other examples of the prior art are not illustrated in the drawings, they have constructions each having a single slot for insertably receiving a single coupling pin so that the coupling pin can shift.
However, these examples of the prior art also produce the second disadvantage according to the first example of the prior art.
The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a coupling structure between a drive shaft and a swash plate assembly in a variable capacity swash plate type compressor, which is so modified that the rotating force of the drive shaft can be transferred to a rotor and the swash plate assembly by substantially equal amounts so as to prevent the frictional of a driving unit as well as prolong life time.
According to an aspect of the invention to obtain the above objects, it is provided a coupling structure between a drive shaft and a swash plate assembly in a variable capacity swash plate type compressor which rotates the swash plate assembly, which is hingeably coupled to one side of a rotor in such a manner that its inclination angle is adjustable, under the rotating force of the drive shaft to reciprocate a piston within a cylinder bore, the coupling structure comprising: the swash plate assembly which includes a drive shaft through-hole for passage of the drive shaft, a hub having a boss with a plurality of pin holes on the outer circumferential surface thereof, and a plate coupled to the outer periphery of the boss and having the piston mounted thereon; the drive shaft which includes a plurality of slots formed thereon in an axial direction to correspond to the pin holes of the hub, the slots communicating and intersecting with each other; and a plurality of coupling pins inserted through the pin holes and the corresponding slots to couple the swash plate to the drive shaft.